border-1px($color)
    position: relative
    &:after
        display:block
        position: absolute
        left: 0
        bottom: 0
        width: 100%
        border-top: 1px solid $color
        content: ''

bg-image($url)
    background-image: url( $url+"@2x.png")
    @media(-webkit-min-device-pixel-ratio:3),(-min-device-pixel-ratio:3)
        background-image url( $url+"@3x.png")       

border-none()
    &:after
        display:none